blenkernel

Renamed get_constraint_target in constraint kernel file to get_constraint_target_matrix since that's what it really does
Moved get_con_target from editconstraint to constraint kernel file and renamed to get_constraint_target

Make scene.c use constraint functions from kernel instead of doing the switch itself (regrouping specific constraint code in one file).

Add LockTrack as an option in the Make Track menu (Ctrl-T)

Adding fun for vortex forces in 3D window, the representation now match the orientation and direction of the force (this is code will need optimisation). I'll probably be slapped for mixing two things in one commit but some function calls needed to be fixed for the new spelling and since this is really isolated code I didn't feel like wasting time getting a fresh copy, doing the changes and then readded this after commiting.

Fixed some warning regarding implicit casts and constants (this last one is a MSVCism where you need to explicitely tell the compiler to use floats with an f. AFAIK, it doesn't affect/bother other compilers).

Removed a useless commented piece of code in readfile (there was an uncommented copy a couple of lines before)